COMMUNICATION TECHNOLOGY D 2 BY DANIEL BOOTH SYNCHRONOUS

COMMUNICATION TECHNOLOGY D 2 BY DANIEL BOOTH

SYNCHRONOUS TRANSMISSION • Synchronous communication is a method of data transfer using continuous steams of data forming singles which are accompanied by regular timing signals. These timing signals are generated by a external clocking mechanism and are used to ensure that both parties are in sync. • It is designed for constant and reliable transmission of data which is time sensitive. Like video streaming. Without data synchronisation data wouldn’t be read in the correct order and would become jumbled.

ASYNCHRONOUS TRANSMISSION • Asynchronous transmission uses start and stop bits to show the start and end of bits. • The bits at the start and end of the transmission alert the receiver to when the first and last character is. • This system is applied when data is sent as individual packets instead of a continuous stream. • These bits has opposite polarity which allows the receiver to understand when each packet is being sent.

ERROR DETECTION • Error detection is used to detect impairments in data while it is transmitted from a source to a destination. • Error detection can ensure delivery of data correctly even if its across a insecure network. • This help lessening the chance of any undetected errors which could scramble the data. • Checksum is an error detection method. • Repetition code also relates to error detection.

ERROR CORRECTION • Error correction is processing the detected errors in the transmitted messages and reconstructing them into there original state. • Systems send out retransmission requests so any incorrect data can be replaced. • This is called ARQ. Which sends a negative acknowledgement if any errors are detected which then gets the receiver to send the message again. • Another method called ECC adds data bits for parity in each message. These bits are then read by the receiver to identify if there any errors in the message.

BANDWIDTH LIMITATION • Bandwidth limitation also known as broadband cap is a transmission limitation which is imposed by the broad band's ISP. • It limits the transfer of data over the internet connection and applies when the channel might be overloaded. • These limits are often so large that they never come close to hitting them but some services like video streaming can easily push the rates over the limit. • This can impair the service for everyone on the network.

BANDWIDTH NOISE • Bandwidth noise is other unwanted signals that interfere with another transmission signal. • This can lower the signal strength and disturb the networks efficiency. • This noise can be caused by radio waves, power lines, bad connections and lightning. • These come in 4 different types: thermal noise, intermodulation noise, cross-talk and impulse noise. • Thermal noise is electron agitation and cannot be removed. • Intermodulation noise is caused by combining several signals which produces new and unwanted frequencies. • Cross-talk noise is caused by magnetic fields of a telecommunication signal when they are both in an adjacent circuit.

CHANNEL TYPES • Channel types consist of telephone, High frequency, radio, microwave and satellite. • Telephone communication is used for speech over distances but is also used for the transmission of other signals. • Telephone is one of the most widespread forms of communication. • High frequency or HF is a electromagnetic frequency designed for radar and radio communication. • The wavelengths spread over 10 to 100 metres and its most commonly used in amateur radio and government/military communication. • Radio is a form of unidirectional wireless transmission which uses radio waves. • Stations are linked to radio networks and they can be reached by a wide audience.

CHANNEL TYPES CONTINUED • Microwave transmission is electromagnetic waves and is used to power forms of communication. • It is used to transmit satellite televisions and for mobile phones. • Satellite communication is used to provide voice and video calling, radio channels, television and even internet. • Satellite communication is capable of providing communication spanning over huge distances and can cope with a huge rand of circumstances that other forms of communication cannot handle.

OTHER ISSUES • Data compression is the process of sizing down data by changing the bit structure to consume less space. • This enables sending data or files over a network or another form of media faster. • Data compression is widely used in computing services because it helps make everything more efficient with no sacrifices having to be made. • Bandwidth is the capacity of a channel or the data transfer speed. • It can be broadly defined as the capacity of a network.